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Photos - 1972 Tube Stock in Original Condition - Mixed

Before 1984 it was not possible to use a Mk I unit and a Mk
II unit of 1972 Stock in the same train. However, in that year, some minor wiring
modifications were carried out to allow this to happen. This photo shows a mixed
train at Edgware (Northern Line) with a 3-car Mk I unit (with unpainted doors) coupled to
a 4-car Mk II unit (with painted doors). The coupling point between the two units
shows the UNDM of the 3-car unit coupled to the DM of the 4-car unit. Photo by B
Hardy.

Following the electrical modifications to allow Mk I units to
couple to Mk II units, on at least one occasion, the two types appeared in the same
unit. In this instance a mixed unit was formed following collision damage to a
couple of cars. The Mk I motor car is coupled into a Mk II unit to replace a
damaged DM car, while the photo illustrates clearly the differences in the bodyside logos.
Photo by B Hardy.

Since refurbishment, a number of trains have been formed with
both types of cars. They can only be distinguished by individual car numbers.